The present invention relates to an electromagnetic contactor and, more particularly, to a structure of an arc extinguishing chamber of an electromagnetic contactor.
With reference to FIGS. 1 to 3, there is shown an arc extinguishing chamber of an electromagnetic contactor previously proposed in the art.
Indicated at reference numeral 1 are two fixed contact elements which have fixed contacts 1a joined thereto. Indicated at reference numeral 2 is a movable contact element which has two movable contacts joined to the two ends thereof which come into and out of contact with the fixed contacts 1a to block an electric current. Indicated at reference numeral 3 is a cross bar which supports the movable contact element 2. Indicated at reference numeral 4 is an insulating base of an insulating substrate which supports the two fixed contact elements 1. Indicated at reference numeral 5 is a box of an insulating substance, which covers the fixed contact elements 1 and the movable contact element 2. Indicated at reference numeral 12 is an arc extinguishing chamber which is defined between the box 5 and the insulating base 4. The box 5 is constructed of a top 5a, two pairs of side walls 5b and 5c, and two pairs of protrusions 5d formed on the paired side walls 5b and facing each other.
Indicated at reference numeral 6 is a commutation electrode which is arranged in the box 5 above the movable contact element 2. This commutation electrode 6 is constructed of flat portions 6a arranged in parallel with the surfaces of the fixed contacts 1a, a pair of generally U-shaped portions 6b formed by extending portions of the flat portions 6a, to the vicinities of the movable contacts 2a, cut-away portions 6c formed by cutting away the generally U-shaped portions 6b at portions facing the movable contacts 2a, and protrusions 6d extending vertically from the leading ends of the flat portions 6a.
Indicated at reference numeral 7 are a plurality of arc extinguishing metal plates which are juxtaposed between the generally U-shaped portions 6b of the commutation electrode 6 and the fixed contact elements 1. These extinguishing metal plates 7 have elastic protrusions 7a at the two ends thereof. Indicated at reference numeral 8 are extinguishing plate supports which are made of an insulating substance. Each of these plate supports 8 is constructed of a pair of side walls 8a, a plurality of grooves 8b formed in the side walls 8a such that the protrusions 7a of the arc extinguishing metal plates 7 may be elastically deformed and press fitted thereinto, a through hole 8c formed therein to receive the corresponding one of the protrusions 6d of the commutation electrode 6, and a wall face 8d closing the sides of the grooves 8b. Indicated at reference numeral 9 is an elastic leaf spring which is retained in a recess 8e formed in the outer side face of one of the side walls 8a of the extinguishing plate supports 8.
Next, the method of assembling the electromagnetic contactor having the aforementioned construction will be explained.
The arc extinguishing metal plates 7 are elastically deformed and press fitted in the grooves 8b of the extinguishing plate supports 8 up to the wall faces 8d of the grooves 8b so that they are fixed in the extinguishing plate supports 8. The protrusions 6d of the commutation electrode 6 are inserted into the through holes 8c of the extinguishing plate supports 8 and are then folded so that the commutation electrode 6 is fixed on the two extinguishing plate supports 8. When the resultant temporary assembly is fitted in the box 5, the leaf springs 9 are elastically deformed between the side walls 8a of the extinguishing plate supports 8 and the paired side walls 5b and 5b, respectively, of the box 5 to retain the extinguishing plate supports 8.
These extinguishing plate supports 8 are retained in the box 5 at the top 5a, the side walls 5b and 5c, and the protrusions 5d of the box 5. Moreover, the protrusions 5d abut against the two end faces of the arc extinguishing metal plates 7 to prevent these metal plates 7 from coming out from their supports 8. With the box 5 being fastened to the insulating base 4 by means of screws (not shown), the extinguishing plate supports 8 are in abutment with the insulating base 4 or the fixed contact elements 1 so that the extinguishing plate supports 8 are retained in the box 5. When the box 5 is removed for replacement of the contacts from the insulating base so that the arc extinguish chamber 12 is opened, as has been described above, the extinguishing plate supports 8 and the commutation electrode 6 in the electromagnetic contactor are retained by the elastic deformation of the leaf springs 9 so that they are prevented from coming out from the box 5. In the normal state in which the box 5 is fastened to the insulating base 4, on the other hand, the extinguishing plate supports 8 and the commutation electrode 6 are retained by the box 5 and the insulating base 4 or the fixed contact elements 1 so that they are fixed with an external force.
Thus, the electromagnetic contactor of the prior art has defects in that it requires the provision of the leaf springs 9 and it requires that the commutation electrode 6 be separately mounted, making the manufacturing costs thereof relatively high.